UV bulbs, etc.

Judy Seigel (jseigel@panix.com)
Wed, 3 Jan 1996 23:02:21 -0500 (EST)

Things have been moving so fast in '96 in the APPL Bowl that some may have
forgotten the incredible proposition that Phil Davis could be right and I
could be wrong in the matter of BL vs. fluorescent bulbs. I understand
further details are due momentarily (and have been advised it's not yet
necessary to take the crow out of the freezer, or just a small one);
meanwhile, here's a footnote:

My cyanotype tests on "regular" fluorescents used Cool White. Davis's gum
& plat. tests used, I gather, Daylight bulbs. The Westinghouse catalog
lists the cool white bulb temperature as 4100 K, the Daylight bulb
temperature as 6500 K, tho I don't know what if any bearing that would
have on the matter.

Westinghouse also has a page of spectral distribution charts (in glorious
color) showing that the cool white bulb has most of its energy at from 550
to 600 nm with a couple of skinny spikes at 400 to 450 nm. However, rudely
and inexplicably, there is no chart or data for the Daylight bulbs (tho we
are given seven others). I'll try to persuade WH to divulge that
information by phone tomorrow, as who knows, it might explain
something....

I believe I did mention making comparisons between the NuArc and the BL
bulbs -- during December, whatever mix I was printing I exposed under a
21-step by both systems for equivalent times (100 units, about 1 3/4 min;
200 units, about 3 min., etc.). Shadow density was always greater *and*
shadow separation better (more steps between D-Max and midtone) by NuArc.

That was visually, I have no reflection densitometer, but reflect that for
printing purposes visual rules anyway, as long as you're not trying to
quantify. (On a single VDB test made en passant, the difference, if any,
was in favor of the BL, tho it was close.)

Incidentally, with thin paper I have read, or thought I read, densities on
the transmission densitometer. Has anyone else tried this?

Judy